using a keyimage with WMS layers

[Emilio Mayorga]

Hi,

I'm using the JPL Landsat and MODIS WMS layers in my application. They 
work great. I'd like to add a legend image, so I crated some png images 
and added class and keyimage statements like this:
CLASS
   KEYIMAGE  "key_modis.png"
END

The legend images showed up fine, but now my WMS layers are showing up 
in gray scale and not in color! What's going on, and how do I fix this? 
Do I do something different when dealing with a WMS layer?

I'm using Mapserver 4.0, with IMAGETYPE PNG24.

Thanks for your help.

-Emilio Mayorga